PROF.. THOMSON AND MR. McQUEEN — REPORT ON THE ALCTONARIANS. lO.T 



The colonies show in each case a substantial trunk which at a distance of 

 2o cm. or less from its base is embraced by a collar of foliate lower branches. 

 These leaf-like branches bear sessile polyps scattered round their margin, 

 while further on the upper surface may be seen twigs, which divide in the 

 corymbose fashion characteristic of the whole colony. These twigs also carry 

 polyps on their tips. 



From the angle between the rising stem and the collar spring one or two 

 branches equal in size to those that are terminal. These branches in their 

 turn break up into terminal corymbs. Beyond the collar, the stem after :i 

 short course divides into two or three main branches, which soon divide up 

 into secondar)' bi-anches supporting the terminal corymbs. The terminal 

 corymbs are all broiiglit more or less to tlie same level, so that the upper 

 surface of the polypariuui is somewhat flattened. A polyp-bundle usually 

 comprises 3 to 8 individual polyps, but the number is very variable. 



The polyp-head is bent more or less at a right or an acute angle to the 

 polyp-stalk. The polyp-head is 0'8 nun. in length and O'.^o mm. in breadtii. 

 The poh'p-staJk is about 1 mm. in length. The anthoeodial spicules are in 

 rows of 3 to 5 pairs, tlie uppermost of which do not projoft lieyond tlir 

 antliocodia. 



The angle of each chevron is a very acute one, giving a somewhat longi- 

 tudinal direction to tlie s))icules of the anthocodia. 



Some variation in colour is to be noted in the anthoeodial spicules. In one 

 of the colonies they are colourless, in another red, while transitional pinkisli 

 spicules are present in a third colony. In the " Stiitzbiindel " there may be 

 one or two projecting spicules. These spicules show very small serrations 

 regularly disposed. Their tip may be quite smooth or with an occasional 

 serration. Their colour varies from a light yellow to a reddish yellow. 



The following measurements were taken of these spicules (length and 

 breadth in millimetres) :—l-5 x 0-03 ; l-25x0-l; 0-8 x 0-03 ; 0-7xO-03. 

 In some of the colonies the size of the projecting '• Stiitzbiindel " spicules 

 approaches nearer to the dimensions of the stout spines which are a feature of 

 the terminal corymbs. These strong spine , which seem to protect and 

 support the polyps on a terminal corymb, generally arise independently of an 

 individual polyp, but sometimes the}' simply take the place of the normal 

 but smaller " Stiitzhundel " spicule. 



Of these stouter spindles the following measurements were taken (length 

 and breadth in millimetres): — •ixO-25; 4x0-2; 3-5x0-15; 3*5 X 0-125. 

 The tentacles are oblong with a few pinnules and without spicules. 



The cortex of the upper branches contains slightly curved spindles with 

 very fine and regularly disposed serrations. 



The following measurements of these spindles were taken (length and 

 breadth in millimetres) :— 4 X 0-2 ; 3-2x0-1; 14x0-5; 1x003. Their 

 colour in o»e specimen is white with a yellowish tinge, in three specimens 



[65] c* 



